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Eccentric resistance training increases and retains maximal strength, muscle endurance and hypertrophy in trained men

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Abstract

The aim of the present study was to evaluate the effects of different resistance training protocols on muscle strength, endurance, and hypertrophy after training and detraining. Thirty-four resistance-trained males were randomized in concentric-only (CONC), eccentric-only (ECC), traditional concentric-eccentric (TRAD) bench press resistance training or control group. The training volume was equalized among the intervention groups. Bench press of 1-repetition maximum (1RM)/body mass, maximum number of repetitions (MNR), and chest circumference were evaluated at the baseline, after 6 weeks of training, and after 6 weeks of detraining. All intervention groups reported significant 1RM/body mass increases after training (CONC baseline: 1.04 ± 0.06, post-training: 1.12 ± 0.08, p < 0.05; ECC baseline: 1.08 ± 0.04, post-training: 1.15 ± 0.05, p < 0.05; TRAD baseline: 1.06 ± 0.08, post-training: 1.11 ± 0.10, p < 0.05). After detraining, only ECC retained 1RM/body mass above the baseline (1.17 ± 0.07, p < 0.05), while CONC and TRAD returned to baseline values. Only ECC improved and retained MNR (baseline: 22 ± 3; post-training: 25 ± 3, and post-detraining: 25 ± 4, p < 0.05 compared with baseline) and chest circumference (baseline: 98.3 ± 2.4 cm, post-training: 101.7 ± 2.2 cm and post-detraining: 100.7 ± 2.3 cm. p < 0.05 compared with baseline), while no significant changes occurred in both CONC and TRAD. The incorporation of eccentric training can be recommended for counteracting the negative effects of detraining or forced physical inactivity.
ARTICLE
Eccentric resistance training increases and retains maximal
strength, muscle endurance, and hypertrophy in trained men
Giuseppe Coratella and Federico Schena
Abstract: The aim of the present study was to evaluate the effects of different resistance training protocols on muscle strength,
endurance, and hypertrophy after training and detraining. Thirty-four resistance-trained males were randomized in concentric-
only (CONC), eccentric-only (ECC), traditional concentric–eccentric (TRAD) bench press resistance training or control group. The
training volume was equalized among the intervention groups. Bench press of 1-repetition maximum (1RM)/body mass, maxi-
mum number of repetitions (MNR), and chest circumference were evaluated at the baseline, after 6 weeks of training, and after
6 weeks of detraining. All intervention groups reported significant 1RM/body mass increases after training (CONC baseline: 1.04 ±
0.06, post-training: 1.12 ± 0.08, p< 0.05; ECC baseline: 1.08 ± 0.04, post-training: 1.15 ± 0.05, p< 0.05; TRAD baseline: 1.06 ± 0.08,
post-training: 1.11 ± 0.10, p< 0.05). After detraining, only ECC retained 1RM/body mass above the baseline (1.17 ± 0.07, p< 0.05),
while CONC and TRAD returned to baseline values. Only ECC improved and retained MNR (baseline: 22 ± 3; post-training: 25 ± 3,
and post-detraining: 25 ± 4, p< 0.05 compared with baseline) and chest circumference (baseline: 98.3 ± 2.4 cm, post-training:
101.7 ± 2.2 cm and post-detraining: 100.7 ± 2.3 cm. p< 0.05 compared with baseline), while no significant changes occurred in both
CONC and TRAD. The incorporation of eccentric training can be recommended for counteracting the negative effects of
detraining or forced physical inactivity.
Key words: bench press, 1RM, maximum number of repetitions, detraining, chest circumference, strength endurance.
Résumé : Cette étude a pour objectif d’évaluer les effets de divers protocoles d’entraînement contre résistance sur la force
musculaire, l’endurance et l’hypertrophie, et ce, a
`la suite d’un entraînement et d’un désentraînement. On répartit aléatoire-
ment 34 hommes entraînés contre résistance dans quatre groupes : développé-couché en miométrie (« CONC »), en pliométrie
(« ECC »), miométrie-pliométrie classique (« TRAD ») et contrôle (« CONC »). On égalise le volume d’entraînement d’un groupe a
`
l’autre. On évalue répétition maximale (« 1RM »)/masse corporelle au développé-couché, le nombre maximal de répétitions
(« MNR ») et le tour de poitrine au début, après 6 semaines d’entraînement et après 6 semaines de désentraînement. Après les
6 semaines d’entraînement, tous les groupes a
`l’entraînement présentent une augmentation significative de 1RM/masse corpo-
relle (CONC début : 1,04 ± 0,06, après l’entraînement : 1,12 ± 0,08, p< 0,05; ECC début : 1,08 ± 0,04, après l’entraînement : 1,15 ±
0,05, p< 0,05; TRAD début : 1,06 ± 0,08, post : 1,11 ± 0,10, p< 0,05). Après la période de désentraînement, seul le groupe ECC
présente un 1RM/masse corporelle au-dessus de la valeur au départ (1,17 ± 0,07, p< 0,05), les groupes CONC et TRAD reviennent
aux valeurs du départ. Seul le groupe ECC améliore et maintient le MNR (début : 22 ± 3; après l’entraînement : 25 ± 3; après le
désentraînement : 25 ± 4, p< 0,05 comparativement au début) et le tour de poitrine (début : 98,3 ± 2,4 cm; après l’entraînement :
101,7 ± 2,2 cm et après le désentraînement : 100,7 ± 2,3 cm, p< 0,05 comparativement au début); dans les groupes CONC et TRAD,
on ne note aucune modification significative. On pourrait recommander l’intégration de l’entraînement en pliométrie pour
contrer les effets négatifs du désentraînement ou de l’inactivité physique forcée. [Traduit par la Rédaction]
Mots-clés : développé-couché, 1RM, nombre maximal de répétitions, désentraînement, tour de poitrine, endurance a
`la force.
Introduction
Resistance training is a great stimulus for increasing muscle
strength and hypertrophy. Traditional resistance training proto-
cols use consecutive eccentric–concentric cycles. However, the
importance of the eccentric phase for increasing muscle strength
was previously highlighted (Dudley et al. 1991). Furthermore, a
meta-analysis showed that eccentric-only versus concentric-only
training induced greater total strength (i.e., the sum of concentric,
isometric, and eccentric peak torque) and muscle hypertrophy
adaptations (Roig et al. 2009). However, the studies considered in
the meta-analysis used different training devices (e.g., isokinetic
dynamometer or dynamic constant external resistance), such as
different training-load volumes. Particularly, matching the differ-
ent training protocols for the session load volume (Coratella et al.
2015a) could help trainers to discriminate the effectiveness of
each training modality. Indeed, when the total work was matched,
similar increases in muscle strength and hypertrophy resulted
after concentric-only versus eccentric-only resistance training (Moore
et al. 2012). In addition, similar relative exercise loads (80% of
concentric vs. eccentric 1-repetition maximum (1RM)), resulted in
similar increases in muscle volume (Franchi et al. 2014). There-
fore, as recently reviewed (LaStayo et al. 2014), the role of exercise
modality for increasing the muscle size remains controversial. In
addition, while eccentric-only and concentric-only based training
protocols have been compared (see (Roig et al. 2009) for a detailed
meta-analysis), the most used method in the field, i.e., traditional
eccentric–concentric exercise, has been rarely compared.
Functional performance improvements are often related to
strength training adaptations. The maximum number of repeti-
Received 6 June 2016. Accepted 8 August 2016.
G. Coratella and F. Schena. Department of Neurological, Biomedical and Movement Science, University of Verona, via Casorati 43, 37131, Verona, Italy.
Corresponding author: Giuseppe Coratella (email: giuseppe.coratella@univr.it.).
Copyright remains with the author(s) or their institution(s). Permission for reuse (free in most cases) can be obtained from RightsLink.
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tions performed using submaximal load has been previously mea-
sured for indicating muscle endurance (Maia et al. 2014;Walker
et al. 2013). Previous studies showed that strength training in-
creased the maximum number of repetitions (Ribeiro et al. 2014;
Walker et al. 2013). The maximum number of repetitions involves
both metabolic (Mujika and Padilla, 2001) and neural adaptations
(Smilios et al. 2010). Compared with concentric-only, the eccentric-only
exercise resulted in greater cortical activation (Fang et al. 2004)
and greater metabolic efficiency (Vogt and Hoppeler 2014). It is
conceivable that the different neural and metabolic engagements
in concentric-only, eccentric-only, or traditional concentric–eccentric
exercises could lead to different adaptations in muscle endurance.
However, to our knowledge, no direct comparison concurrently
investigated the effects of different resistance exercise modalities
on muscle endurance.
The cessation of training (i.e., detraining) is linked to decreases
in both physiological and functional muscle characteristics. Pre-
vious studies showed that traditional resistance training retained
maximal strength increases (Correa et al. 2013;Fatouros et al.
2005). Similarly, previous studies showed that both eccentric-only
(Housh et al. 1996a) and concentric-only (Housh et al. 1996b) resis-
tance training protocols both increased and retained maximal
strength. The mechanisms underlying the muscle strength, hy-
pertrophy, and endurance retention could depend on both neural
(Fang et al. 2004) and cellular (Bruusgaard et al. 2010) factors.
Eccentric-only exercise is known to induce muscle damage and to
confer muscle protection (i.e., the repeated bout effect) (Coratella
and Bertinato 2015). Such a long-lasting protection involved de-
layed extra-cellular matrix adaptations, which can be partially
responsible even for the retention of the training-induced adap-
tations (Hyldahl et al. 2015).
The bench press is one of the most common and effective exercises
for increasing upper body strength and hypertrophy. Although the
bench press involves several upper body muscles, increases in the
size of the chest muscles is one of the main training-induced adap-
tations (Yasuda et al. 2010). In addition, the chest circumference, the
upper arms cross-sectional area and the percentage of fat are all
predictors for the bench press 1RM and they can be used as indirect
markers of muscle hypertrophy (Mayhew et al. 1991). Among these
aforementioned markers, the chest circumference is the most easily
assessable in field, as it does not require the use of laboratory devices
or sophisticated formulas.
Several athletes or amateurs incorporate resistance training in
their workouts. The bench press is included in most strength or
fitness programs, traditionally exercised in concentric–eccentric
protocols. However, the concentric-only or eccentric-only training
protocols are rarely performed within a field-based context, while
they have been largely investigated in laboratory settings. There-
fore, the primary aim of the present study was to evaluate the
retention of maximal strength, maximum number of repetitions,
and chest circumference adaptations after 6 weeks of detraining
subsequent to concentric-only, eccentric-only, or traditional concentric-
eccentric bench press training in resistance-trained men. The
secondary aim was to evaluate if the training-induced changes
depend on the exercise modalities. In the first instance, it has
been conceived that eccentric-only training can successfully re-
tain the training-induced adaptations. In addition, it has been
conceived that despite the different training modalities, the matched-
volume protocols can lead to similar training-induced adaptations.
Materials and methods
Study design
This study was a parallel, 4-groups, pre-/post-training, random-
ized controlled trial. Using a restricted blocked randomization
(computer-generated sequence), the participants were random-
ized into 4 groups: concentric-only (CONC), eccentric-only (ECC),
traditional concentric–eccentric training (TRAD) and control group
(CON). One of the researchers without any contact or knowledge of
the participants completed the allocation and randomization of
groups. Therefore, no allocation concealment mechanisms were
necessary.
Procedures
The present investigation lasted 15 weeks. Participants were
evaluated at week 1, week 8, and week 15. The intervention period
lasted from week 2 to week 7 and the detraining period from
week 9 to week 14. During both training and detraining, partici-
pants were asked to refrain from any other form of strenuous
physical activity. In addition, the detraining period corresponded
to the summer holidays, to avoid as much as possible any chance
of training. On a weekly basis, the operators reminded partici-
pants to avoid any other form of resistance training for the entire
period of the study. Both training and testing sessions were as-
sessed using a flat bench press (Technogym, Cesena, Italy).
Participants
Thirty-four healthy, resistance-trained, sport-science student
males with a minimum of 3 years of experience in resistance
training (age: 26 ± 3.7 years; body mass: 85.4 ± 11.4 kg; height 1.83 ±
0.11 m) volunteered for this study. We included only males who
were able to perform a bench press 1RM equal or greater than
their body-mass (Table 1). Upper joint diseases as well as muscular
injuries were considered as exclusion criteria. In addition, we
excluded males who regularly used supplementation in the pre-
vious 3 months. The participants signed a written informed con-
sensus, which described the procedures in detail, and the Ethics
Committee of the University of Verona approved the present
study.
Intervention
The training volume load was equalized among the 3 interven-
tion groups. We matched the repetition number, the training load
(considered as percentage of 1RM), and the time under tension was
3 s and it was equal for each phase (concentric or eccentric)
(McBride et al. 2009). Therefore, for each training session, ECC
performed 5 sets × 6 repetitions at 120% of 1RM; CONC performed
6 sets × 7 repetitions at 85% of 1RM; TRAD performed 4 sets ×
5 repetitions at 90% of 1RM at the bench press, while CON did not
train. During each repetition performed in ECC, 2 operators lifted
the bar to relieve each participant from the concentric phase
(Coratella et al. 2015b). Similarly, 2 operators lowered the bar dur-
ing each repetition performed in CONC to relieve each participant
from the eccentric phase (Housh et al. 1996b). Participants in
TRAD performed both phases without the help of any operator.
Table 1. Anthropometric and performance characteristics at baseline are reported for each group.
Body
mass (kg) Height (m) 1RM (kg) 1RM/body mass
Maximum
Nrepetitions
Chest
circumference
ECC 86.6±14.3 1.84±0.09 93.8±18.3 1.08±0.04 22.1±3.2 98.3±5.6
CONC 84.6±8.2 1.82±0.08 88.6±9.9 1.05±0.06 25.4±3.8 101.2±5.0
TRAD 84.4±14.2 23.9±4.2 88.7±12.4 1.04±0.08 24.0±4.7 102.8±10.2
CON 86.1±9.2 26.1±4.9 89.0±6.2 1.04±0.06 24.4±3.2 98.3±5.6
Note: No significant between-group difference was found. 1RM, 1-repetition maximum; CON, control; CONC,
concentric-only; ECC, eccentric-only; TRAD, traditional concentric–eccentric.
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Each set was separated by 3 min of passive recovery. The interven-
tion lasted 6 weeks, twice a week, for a total of 12 sessions. Each
session was separated by at least 2 days. After the post-training
testing session, participants did not train for 6 weeks.
To keep the exercise technique similar among the participants,
participants were instructed to exercise using the same relative
bar handgrips distance. Therefore, hands were placed on the bar
at a distance that facilitated approximately a 90° angle between
arms and forearms, when the bar is on the chest, approximately
one-half length of sternum.
Bench press 1RM/body mass
The bench press 1RM was tested on a gym device (Flat bench
press, Technogym, Cesena, Italy). The testing protocol started with a
standardized warm-up, consisting of 2 sets × 15 repetitions with a
load equal to 50% of the person’s body mass. This protocol was
based on the following formula (Brzycki 1993):
predicted 1RM load/1.0278 (0.0278 · n)
where the load is in kg, the 90% of the predicted 1RM was used as
an initial 1RM attempt, and nis the number of executed repeti-
tions. Afterwards, additional load of 2.5 kg was added until sub-
jects failed to lift the bar. Two minutes of passive recovery separated
each trial. Each participant received standardized encourage-
ments by the operators. Bench press 1RM/body mass was recorded
and analyzed.
Bench press maximum number of repetitions
Based on 1RM measurements, after 60 min of passive rest, par-
ticipants performed a single set up to failure of bench press at 50%
of their previously recorded 1RM. They were instructed to main-
tain the time under tension equal to 1.5 s for both concentric and
eccentric phases. A visual chronometer feedback was provided to
help the participants to maintain the proper repetition pace. The
task ended when participants failed to properly lift the bar for
2 consecutive repetitions within the set time under tension. Op-
erator provided standardized encouragements to each participant.
Chest circumferences
The participants stood with arms slightly abducted, permitting
the tape to be passed around the chest. The chest girth was mea-
sured at the level of mesosternal. The measurement was taken at
the end of normal respiration (Stewart et al. 2001). Each measure-
ment was repeated twice and the mean was inserted in data anal-
ysis. If the 2 measures differed by more than 5%, a third measurement
was performed. Same operator performed all measurements.
Statistical analysis
The statistical analysis was performed using IBM SPSS (version
20.0; IBM Corp., Armonk, N.Y., USA). The normality of the distri-
bution was analyzed using Shapiro–Wilk test. The sphericity as-
sumption was analyzed using the Mauchly test. Test–retest reliability
was measured using Cronback-index. The variations of the de-
pendent parameters (bench press 1RM/body mass, maximum
number of repetition and chest circumference) were analyzed
using mixed-factorial repeated measures ANOVA (time × group).
Post hoc analysis using Bonferroni’s correction was then per-
formed to calculate main effect for group (4 levels: ECC, CONC,
TRAD, and CON) and time (3 levels: baseline, post-training, and
after detraining). Significance was set at p< 0.05. Data are re-
ported as means ± SD and change scores are reported with confi-
dence interval (CI) 95% and
2
.
Results
Bench press 1RM/body mass
A time × group interaction (p< 0.001) was found for the bench
press 1RM/body-mass. There was a main effect for time (p< 0.001)
and a trend (p= 0.055) for group. Post hoc analysis showed 1RM/
body-mass increases over time from baseline to post-training in
CONC (0.07 ± 0.01, CI95% 0.04 to 0.10, p< 0.001,
2
= 0.589), in ECC
(0.07 ± 0.01, CI95% 0.04 to 0.10, p< 0.001,
2
= 0.597), and in TRAD
(0.05 ± 0.01, CI95% 0.02 to 0.08, p= 0.001,
2
= 0.437) (Fig. 1).
However, 1RM/body mass increases remained greater than base-
line after detraining only in ECC (0.09 ± 0.01, CI95% 0.05 to 0.012,
p< 0.001,
2
= 0.698), while both CONC and TRAD returned to
values similar to baseline. CON did not show any change. No
between-group differences resulted at baseline. After training,
1RM/body mass resulted greater in ECC compared with CON (0.11 ±
0.04, CI95% 0.01 to 0.20, p= 0.027,
2
= 0.263). After detraining ECC
resulted in greater 1RM/body mass compared with CON (0.13 ±
0.04, CI95% 0.02 to 0.024, p= 0.011,
2
= 0.349) and to CONC (0.11 ±
0.04, CI95% 0.01 to 0.21, p= 0.034,
2
= 0.174) but not to TRAD,
(0.11 ± 0.04, CI95% –0.00 to 0.21, p= 0.058,
2
= 0.111).
Maximum number of repetitions
A time × group interaction (p= 0.042) was found for the bench
press maximum number of repetitions. There was a main effect
for time (p= 0.017), but not for group (p= 0.554). Post hoc analysis
showed increases over time from baseline to post-training only in
ECC (3.0 ± 0.7, CI95% 1.1 to 4.8, p= 0.001,
2
= 0.412) (Fig. 2), In
addition, such increases were retained after detraining compared
with baseline (3.1 ± 1.0, CI95% 0.5 to 5.6, p= 0.014,
2
= 0.304).
Neither CONC, TRAD, nor CON showed any change.
Chest circumference
Test–retest reliability resulted in a Cronbach-= 0.910. A time ×
group interaction (p= 0.014) was found for the chest circumfer-
ence. There was a main effect for time (p< 0.001) but not for group
(p= 0.471). Post hoc analysis showed increases over time from
baseline to post-training only in ECC (3.3 ± 0.6, CI95% 1.7 to 4.8,
p< 0.001,
2
= 0.488) (Fig. 3). The chest circumference remained
above the baseline in ECC after detraining (2.4 ± 0.6, CI95% 0.8 to
3.8, p= 0.001,
2
= 0.417). Neither CONC, TRAD, nor CON showed
any significant change.
Discussion
The present study investigated the effectiveness of different
bench press resistance training protocols on muscle strength, en-
Fig. 1. The time-course of bench press 1RM/BM is shown for each
intervention group. Compared with baseline, greater 1RM/BM resulted
in ECC, CONC, and TRAD post-training. After detraining, 1RM/BM
resulted significantly greater than baseline only in ECC; CONC, and
TRAD showed significant 1RM/BM decreases compared with post-training,
resulting in values similar to baseline. 1RM/BM, 1-repetition maximum/
body mass; CON, control; CONC, concentric-only; ECC, eccentric-only;
TRAD, traditional concentric–eccentric. *, p< 0.05; †, p< 0.05
compared with CON post-training; ‡, p< 0.05 compared with CONC
and CON detraining.
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durance, and hypertrophy increases and retention. The primary
outcomes highlighted that ECC was the only training modality
that preserved the increases in maximum strength after 6 weeks
of detraining in resistance-trained men. In addition, only ECC
improved and retained the maximum number of repetitions at
50% of 1RM and the chest circumference. Finally, all the training
protocols, matched for the volume load, similarly improved the
bench press 1RM/body mass in trained men.
The present outcomes highlighted that only ECC increased and
retained the bench press 1RM/body mass after detraining. The
superiority of the eccentric-only versus concentric-only or tradi-
tional resistance training in strength retention is debatable. The
importance of eccentric exercise for promoting the retention of
strength gains has been documented in literature. Eccentric-only
training was shown to be a great stimulus for retaining strength
increases (Housh et al. 1996a). In addition, knee extensors isokinetic
peak torque remained above the baseline values after 3 months
of detraining following 10 weeks of eccentric-only training (Blazevich
et al. 2007). Furthermore, after concentric-only training versus
traditional training, the detraining seemed to have a detrimental
effect for the strength gain resulted after the concentric-only
training (Dudley et al. 1991). However, other studies showed that
strength retention is not a peculiarity only of the eccentric-only
training. In the same above-mentioned study, the authors also
showed that concentric-only training was able to retain strength
increases after detraining (Blazevich et al. 2007). Similarly, the
knee extensors 1RM improvements induced by concentric-only
training were unaffected by 8 weeks of detraining (Housh et al.
1996b). In addition, traditional resistance training was shown to
be a proper stimulus for increasing the muscle strength and for
retaining it after detraining (Correa et al. 2013). Due to such mul-
tiplicity, it is not possible to state that the strength retention
could depend on the exercise performed during the training pe-
riod. However, our results seemed to confirm the superiority of
ECC compared to CONC and TRAD, in agreement with the studies
that supported the superiority of eccentric-only exercise.
The mechanisms underlying the overall strength retention are
not fully understood. A possible explanation could be that during
the training period, additional nuclei from the satellite cells are
added into the muscle fibres throughout the fusion process, stim-
ulating the increasing in protein synthesis (Bruusgaard et al.
2010). After the end of the training, such nuclei remained into the
muscle cell for at least 3 months. In such a way, the muscle is able
to develop a sort of “memory”, useful both to prevent atrophy
(and consequent decreases in strength) and to get quicker adapta-
tions after retraining (Bruusgaard et al. 2010). However, such
mechanism has been recently debated (Gundersen 2016) and it
cannot explain the greater strength retention that resulted in
ECC. The extra-cellular matrix can be defined as a bridge for the
transmission of force from the myofibres to the tendons (Grounds
et al. 2005). Interestingly, the extra-cellular matrix plasticity could
play a key role for the strength retention. While no difference in
collagens’ upregulation gene responses occurred after 4 days of
concentric-only versus eccentric-only short-term training (Heinemeier
et al. 2007a), a more recent study showed for the first time that the
extra-cellular collagens’ upregulation occurred 27 days (but not
2 days) after repeated eccentric-only exercise (Hyldahl et al. 2015).
It can be speculated that such a delayed stimulus could be par-
tially responsible for the strength retention that resulted only in
ECC. A further explanation involves neural adaptations. Neural
cortical adaptations have been suggested to be partly responsible
for strength retention, although the physiological training in-
duced changes could be dissipated (Gabriel et al. 2006). Compared
with concentric-only, eccentric-only exercise involves larger cor-
tical areas during maximal tasks (Fang et al. 2004). As hypothe-
sized by the same authors, increasing the neural control of the
eccentric exercise contributes to avoid muscle damage (Fang et al.
2004). Indeed, it is known that performing eccentric-only exercise
protects muscle from further damage following the first session
(Coratella and Bertinato 2015). The repeated bout effect can last up
to several months, during which participants did not train
(Nosaka et al. 2001). Therefore, it can be speculated that ECC could
be involved in greater and longer lasting neural cortical adapta-
tions. Finally, it has been shown that strength retention depends
on the intensity performed during the resistance training (Fatouros
et al. 2005). In addition, resistance training showed similar electro-
myography (EMG) signal increases after eccentric-only or concentric-
only isokinetic training (Carvalho et al. 2014). However, the same
authors observed more significant neural adaptations after eccentric-
only compared with concentric-only, probably depending on the
greater torque exerted during ECC. Although both TRAD and
CONC were exercised at high-intensity loads, the greater supramaximal-
intensity load performed in ECC could have favourably influenced
the strength retention. In summary, it can be speculated that the
strength retention, which resulted only in ECC, could depend on
both cellular and neural long-lasting adaptations.
Similarly to the previous data, only ECC showed increases in
chest circumference, which remained significantly above the
baseline after detraining. The anabolic effect of resistance train-
ing depends in first instance on its capacity to stimulate anabolic
Fig. 2. The time-course of maximum number (N) of repetitions is
shown for each intervention group. Post hoc comparison showed
that only ECC increased and retained maximum number of
repetitions after both post-training and detraining compared with
baseline. CON, control; CONC, concentric-only; ECC, eccentric-only;
TRAD, traditional concentric–eccentric. *, p< 0.05.
Fig. 3. The time-course of chest circumference is shown for each
intervention group. Post hoc comparison showed that only ECC increased
and chest circumference after both post-training and detraining
compared with baseline. CON, control; CONC, concentric-only; ECC,
eccentric-only; TRAD, traditional concentric–eccentric. *, p< 0.05.
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hormones such as growth hormone or bioavailable testosterone.
However, the postexercise elevation in hormones is still debatable
and their role still remains to be proved (Schoenfeld 2013). It has
been showed that traditional versus enhanced-eccentric resis-
tance exercise (Yarrow et al. 2007) or short-term training (Yarrow
et al. 2008) led to a similar growth hormone and bioavailable blood
concentration increases in untrained men. However, enhanced-
eccentric training resulted in lower volume load compared with
the traditional protocol (Yarrow et al. 2008). Therefore, similar GH
and BT serum concentrations were found with different load vol-
umes. It can be speculated that equalizing the load volume could
have resulted in a greater anabolic response in ECC. However, it
remains to be proved. In addition, greater insulin-like growth
factor and mechano-growth factor gene expressions were induced
by eccentric-only compared with concentric-only short-term training
(Heinemeier et al. 2007a). Similarly, the same abovementioned
authors found decreases in muscle myostatin messenger RNA after
eccentric-only versus concentric-only training (Heinemeier et al.
2007b). Conversely, comparing eccentric-only versus concentric-
only training, other studies did not show any differences in pro-
tein synthetic response (Franchi et al. 2015) or protein kinase B
and p70 s6 kinase (Cuthbertson et al. 2006) gene expressions. In
addition, it is well known that the aforementioned mechanisms
can last up to several weeks after the end of the training (Bruusgaard
et al. 2010). Therefore, the possible mechanisms underlying the
different hypertrophy responses and retention induced by eccentric-
only versus concentric-only or traditional training modalities are
still controversial.
The maximum number of repetitions exercised at 50% 1RM in-
creased after ECC training and it remained above the baseline
level after detraining. Focusing on the detraining, it has been
shown that the central neural drive is reduced within a fatiguing
strength-endurance task (Walker et al. 2012). In addition, during a
submaximal task, the EMG activity increases for maintaining the
demanded power output, with a reduction in efficiency (Smilios
et al. 2010). Finally, the eccentric contraction resulted in larger
cortical activation (Fang et al. 2004). Therefore, it can be specu-
lated that ECC could have led to an increased and longer lasting
neural drive, which can also result in a greater efficiency turned
into a later fatigue. Furthermore, compared with the maximal
strength, the maximum number of repetition depends also on
metabolic and energetic factors. The enzymatic activity, the mus-
cle capillarization, the mitochondrial ATP production, the muscle
fibre characteristics, and the myoglobin concentration are all in-
volved in the enhancement or the detriment of the submaximal
continuous force production (Mujika and Padilla, 2001). While
several studies showed a greater number of maximum repetitions
after strength training using different traditional exercise proto-
cols (Ribeiro et al. 2014;Maia et al. 2014;Walker et al. 2013), it is
not proven if the intensity or the contraction modality exercised
during the training could influence it. It can be speculated that
ECC could have improved the mechanical efficiency and conse-
quently the muscle endurance (Vogt and Hoppeler 2014). To our
knowledge, no study concurrently compared the retention of the
maximum number of repetitions in response to different resis-
tance training modalities. Hence, it is hypothesized that both
neural and metabolic stimuli could be involved in both increasing
and specially retaining the maximum number of repetitions.
The present outcomes showed similar training-induced strength
increases after all type of intervention. The greater effectiveness
of eccentric-only versus concentric-only training has already been
reviewed (Roig et al. 2009). However, the studies selected for the
meta-analysis used different session intensities or volume. In ad-
dition, traditional resistance training is also known to be effective
for promoting strength increases (Correa et al. 2013). However, the
volume load plays a key role in the strength training-induced
adaptations (Franchi et al. 2014). Therefore, although there were
different exercise modalities and intensities used in the present
study, it is confirmed that similar volume loads induced similar
adaptations (Coratella et al. 2015a).
The present investigation appears to include some limitations.
First, we matched the training volume among the intervention
groups using the volume load method (i.e., repetitions × external
load (kg)). Total work (i.e., force (N) × displacement (m)) is the most
appropriate method to quantify resistance exercise volume, al-
though it is acknowledged that it is not easy to assess (McBride
et al. 2009). However, the same authors stated that the major
limitations of volume load occur when external load is absent,
(e.g., power exercise protocols) and when time under tension is
not taken in account. By equalizing the time under tension (3 s for
concentric and eccentric phases), the volume load could be a rea-
sonable alternative to total work. Second, we did not record the
nutritional intake during the entire investigation period. Even if
nonsignificant body mass changes occurred, it may have con-
founded the results. Third, we did not record muscle damage
markers. Exercise-induced muscle damage could have impaired
the participant’s capacity to properly perform the resistance
training, particularly in the first training sessions. However, a
previous study showed that resistance-trained men were slightly
affected by muscle damage occurring after the bench press exer-
cise (Meneghel et al. 2014). Therefore, we are confident that all
training sessions were properly performed. Fourth, detecting the
EMG signal can provide news insight the muscle activity adapta-
tions after training and particularly detraining. Finally, we tested
the strength changes using concentric 1RM. It is acknowledged
that such a test could not be specific for the eccentric-only exer-
cise, as the eccentric-1RM could be. Therefore, the lack of between-
groups differences in strength training-induced adaptations could
possibly depend also on a nonspecific eccentric test.
In summary, we showed that ECC was the only resistance pro-
tocol able to retain the strength increases after 6 weeks of detrain-
ing in resistance trained men. In addition, only ECC increased and
preserved the maximum number of repetitions and the chest
circumference.
Conflict of interest statement
The authors declare that there are no conflict of interest.
Acknowledgements
Authors are grateful to all participants that volunteered for this
study. Authors want to thank Andrea Bertinato BSc for his pre-
cious help in data collection.
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... Therefore, submaximal loading may be an easier approach, which generates less post-exercise damage and lower injury risk, while providing similar benefits, as showed by our results. It also should be noted that accentuated eccentric loading elicited an improvement in fatigue resistance (Coratella & Schena, 2016). This was evidenced by Walker et al. (2016Walker et al. ( , 2020 who found significant improvements in the unilateral knee extension repetition-to-failure test (~28%) after supramaximal EO-RT with high concentric loads. ...
... These changes may be due to the fact that the eccentric contraction leads to an increased and longer neural drive, independently of the load magnitude (Wagle et al., 2017). Which in turn could improve the mechanical efficiency and consequently local muscle endurance (Vogt & Hoppeler, 2014;Coratella & Schena, 2016). Therefore, the use of low concentric intensities and a submaximal accentuated eccentric loading might be a good strategy for all those people and athletes who seek to improve their local muscular endurance. ...
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... The neuromuscular uniqueness of the eccentric vs. concentric contraction [18][19][20], and the additional use of the semi-passive and passive sarcomeres proteins [36][37][38], make the eccentric contraction less expensive, with a lower nRMS recorded for a given load [39]. Therefore, using a constant external load is a sub-stimulus for the eccentric phase, since it is tailored on the concentric capacity [40]. However, the present results show that the biceps curl variations examined may have different neural patterns during the ascending or descending phase, so it would be relevant to plan all of them in resistance training practice. ...
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The present study investigated the excitation of the biceps brachii and anterior deltoid during bilateral biceps curl performed using the straight vs. EZ barbell and with or without flexing the arms. Ten competitive bodybuilders performed bilateral biceps curl in non-exhaustive 6-rep sets using 8-RM in four variations: using the straight barbell flexing (STflex) or not flexing the arms (STno-flex) or the EZ barbell flexing (EZflex) or not flexing the arms (EZno-flex). The ascending and descending phases were separately analyzed using the normalized root mean square (nRMS) collected using surface electro-myography. For the biceps brachii, during the ascending phase, a greater nRMS was observed in STno-flex vs. EZno-flex (+1.8%, effect size [ES]: 0.74), in STflex vs. STno-flex (+17.7%, ES: 3.93) and in EZflex vs. EZno-flex (+20.3%, ES: 5.87). During the descending phase, a greater nRMS was observed in STflex vs. EZflex (+3.8%, ES: 1.15), in STno-flex vs. STflex (+2.8%, ES: 0.86) and in EZno-flex vs. EZflex (+8.1%, ES: 1.81). The anterior deltoid showed distinct excitation based on the arm flexion/no-flexion. A slight advantage in biceps brachii excitation appears when using the straight vs. EZ barbell. Flexing or not flexing the arms seems to uniquely excite the biceps brachii and anterior deltoid. Practitioners should consider including different bilateral biceps barbell curls in their routine to vary the neural and mechanical stimuli.
... Toutefois, nous ne savons pas à ce jour si l'usage chronique d'exercices excentriques représente une stratégie d'entraînement plus efficace que l'entraînement concentrique pour initier des réponses hypertrophiques du muscle trié squelettique. Des études ont montré une augmentation plus importante de la circonférence du membre (CORATELLA et SCHENA, 2016;KOMI et BUSKIRK, 1972) ou de la ACSA (HIGBIE et collab., 1996;VIKNE et collab., 2006) 15 -Représentation schématique de la contribution relative des adaptations neuromusculaires dans l'amélioration de la capacité de production de force musculaire à l'entraînement contre-résistance. Cette dernière est représentée en bleu. ...
Thesis
La survenue d’altérations neuromusculaires et musculo tendineuses lors d’épreuves de course à pied de fond s’avère être délétère sur la capacité de performance d’endurance et la période de récupération des athlètes. Par ailleurs, la sévérité de ces perturbations peut être exacerbée par les caractéristiques du terrain, et plus particulièrement par la présence de dénivelé négatif. En course à pied de descente, l’amplitude plus importante de ces altérations est sous-tendue par la prédominance du régime de contraction excentrique à l’exercice. Dès lors, la course à pied de descente constitue un challenge pour les coureurs dans leur quête d’excellence athlétique, aussi bien à l’entraînement que lors d’épreuves compétitives. L’exploration de stratégies préventives, ayant pour objectif de mieux tolérer les sections de course à pied en descente, apparaît donc pleinement justifiée dans le domaine de l’optimisation des réponses adaptatives en course à pied. Dans ce contexte, une première analyse prospective de la littérature a focalisé sur l’exploration des stratégies de répétitions de sessions (c.-à-d., usage chronique de la course à pied en descente) et du port in situ de textiles vestimentaires à visée ergogénique (e.g., textiles de compression et réflecteurs de rayons infrarouges lointains). Étant donné que l’usage chronique de la course à pied en descente pourrait également permettre l’instauration d’adaptations bénéfiques sur la capacité de performance des athlètes, il convenait au préalable de préciser les adaptations neuromusculaires et musculo-tendineuses à l’entraînement de course à pied en descente. Ainsi, les objectifs du travail de thèse étaient de caractériser les adaptations neuromusculaires et musculo-tendineuses à l’entraînement de course à pied en descente d’une part, et d’enrichir nos connaissances sur l’apport de stratégies préventives dans le domaine de la course à pied de fond, d’autre part. Les résultats de ce travail ont montré que : (i) l’entraînement de course à pied en descente (4 semaines) peut instaurer de rapides adaptations neuromusculaires (e.g., gains de force, hypertrophie musculaire) et tendineuses (par exemple, augmentation de la raideur du tendon patellaire), sans pour autant atténuer la sévérité des perturbations neuromusculaires à l’issue d’une session de course à pied en descente ; (ii) que le port de textiles de compression à l’exercice peut exercer un « effet protecteur dynamique » sur les groupes musculaires compressés, sans pour autant atténuer les perturbations de la capacité de performance d’endurance des athlètes ; et (iii) que le port de textiles réflecteurs de rayons infrarouges à l’exercice pourrait générer certains effets ergogéniques mais que la compréhension de leurs effets reste à ce jour globalement limitée.
... The realisation of delayed training effects following eccentric training may require considerable time (Baroni et al., 2013;Coratella & Schena, 2016;Leong et al., 2014;Shepstone et al., 2005). As such, high-load eccentric training with fast lengthening actions is prescribed with lower volumes during the 4-week pre-competition phase to allow for adequate recovery while maintaining high levels of force production. ...
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Successful performances in rugby league require the ability to engage in repeated contact efforts with minimal recovery while maintaining a high running intensity. The capacity to express high levels of time-limited force appears to underlie many important physical attributes required to meet the repeated-effort demands of rugby league play. If appropriately periodised and integrated into the training plan, resistance exercise that sufficiently loads the eccentric phase of movement may provide a beneficial stimulus to improve players' force-generating capacity. Comprehensive reviews relating to the adaptive effects of eccentric training and the methods most commonly prescribed in practical environments are available and may provide context for applying these strategies. However, no literature to date has specifically discussed the planning and programming of eccentric resistance exercise to enhance force production characteristics in elite athletes. Therefore, this narrative review focuses on the periodisation of eccentrically-integrated resistance training during a 17-week National Rugby League pre-season phase. To help guide programming during the pre-season period, the 17-week timeline is divided into several phases (i.e., general preparation, special preparation, active rest, and pre-competition). Within the periodised model, eccentric exercise parameters (i.e., volume, load [% 1RM]) are manipulated to progressively increase the rate of muscle lengthening velocity over the pre-season phase and sequentially elicit changes in muscle-tendon properties and neural function that culminate in improving muscular strength expression.
... ECCst exercise can improve skeletal muscle performance with lower oxygen requirement compared to CONst exercise (Perry, Betik, Candau, Rouillon, & Hughson, 2001). ECCst exercises include isoinertial or isokinetic segmental contractions (Coratella, & Schena, 2016). Skeletal muscle generates force either by shortening (concentrically) or lengthening (eccentrically). ...
Article
The aim of present study was to examine the effects of eccentric and concentric training applied to football players on some motor characteristics. A total of 23 university students playing soccer participated in the study voluntarily. Subjects were randomly divided into two groups; complex (ECCst) and contrast (CONst) training protocols. During 12- weeks, ECCst and CONst training groups performed strength training in addition to soccer training 3 days a week, over 7 hours (4-5 units). On the first day, one repetition maximum (1RM) strength tests of all subjects were measured respectively. On the second day, all athletes’ height, body weight, body fat ratio, vertical jump, and sprint (20 m) tests performance tests were measured at the beginning and end of the 12-weeks study. As a result, although there was a statistically significant difference between the pre and post (lying leg curl, machine abduction, machine adduction 1RM) and vertical jump test of the subjects in both ECCst and CONst training group in terms of time effect, a significant difference was found in favor of the ECCst in the group x time interaction of ECCst training compared to CONst (p0.05). As a result revealed that 12-weeks ECCst more effective than CONst in improving lower extremity strength and vertical jump of soccer players. There were similar increases in both ECCst and CONst in 1RM leg extension and 20m sprint.
... Weight training significantly increases the endurance of archery athletes . Based on research (Coratella & Schena, 2016;Decheline et al., 2020;Nyberg et al., 2016;Rohmansyah et al., 2020;Wijaya et al., 2020) the ability of a muscle or a group of muscles to exert external force repeatedly over a long period describes muscle endurance which means the athlete was fit. Therefore, muscle fitness plays an essential role in the longterm development stage of athletes/in the duration of the match which is quite time-consuming. ...
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Restrictions on community activities due to the spread of the Covid-19 virus have changed sports in Indonesia, forcing athletes to practice independently in their respective homes with training programs created by coaches. This study aims to find out the effect of circuit body weight training on arm muscle endurance and archery accuracy of archery athletes. This research is an experimental method of one group pretest-posttest design. This study employed purposive sampling with the criteria of elite archery athletes, still in high school, male, and willing to participate. Total of 12 athletes was given treatment with 8 movements for 16 meetings. The instrument is a holding bow digit test for arm muscle endurance, while archery accuracy uses 50 meters of archery. The collected data were examined for normality and homogeneity, then followed with t-test with the result that t count = 0.00 less than t (0.05). Based on the results, it is concluded that circuit bodyweight training positively improves arm muscle endurance and accuracy of archery athletes. Therefore, giving circuit bodyweight training can be used as a recommendation for physical exercise to increase arm muscle endurance and archery accuracy in archery athletes.
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Introducción: el basquetbol es un deporte en el que se manifiestan acciones intermitentes e intensas durante el juego, por ello, la capacidad de producir potencia muscular es determinante. Objetivo general: comparar los efectos de un entrenamiento excéntrico y uno concéntrico sobre la potencia muscular (PM) y fuerza máxima (FM) en basquetbolistas. Materiales y métodos: participaron ocho atletas entre 16-18 años, quienes conformaron la selección de Chihuahua, que participó en los juegos nacionales 2021. El entrenamiento duró cinco semanas, con una frecuencia de dos sesiones semanales, las cuales, se llevaron a cabo cada 72 horas; los ejercicios fueron sentadilla y press banca. Los participantes fueron divididos aleatoriamente en dos grupos, uno de ellos, solamente realizó la fase excéntrica (GE) y, el otro, la concéntrica (GC). Se midió la PM, con el salto contra movimiento (CMJ), lanzamiento de balón (LB) y al 30 % de la carga máxima en sentadilla y press banca; la FM, mediante la 1RM. Resultados y discusión: hubo mejorías en el CMJ (P=0,01), la PM en sentadilla (P=0,00) y FM (P=0,00), en ambos grupos; el press banca solo aumentó en el GC (P=0,05); por su parte, el LB no presentó cambios; no hubo diferencias al comparar los grupos entre sí. Conclusión: ambos entrenamientos producen efectos parecidos para el desarrollo de la PM y FM en este grupo de jugadores.
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The purpose of this study was to investigate the effect of hypertrophy-type resistance training (RT) on upper limb fatigue resistance in young adult men and women. Fifty-eight men (22.7±3.7 years, 70.6±9.3 kg, and 176.8±6.4 cm) and 65 women (21.6±3.7 years, 58.8±11.9 kg, and 162.6±6.2 cm) underwent RT for 16 weeks. Training consisted of 10-12 whole body exercises with 3 sets of 8-12 repetitions maximum performed 3 times per week. Before and after the RT intervention participants were submitted to 1RM testing, as well as a fatigue protocol consisting of 4 sets at 80% 1RM on bench press (BP) and arm curl (AC). The sum of the number of repetitions accomplished in the 4 sets in each exercise was used to indicate fatigue resistance. There was a significant (p
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We recently reported that the greatest distinguishing feature between eccentric (ECC) and concentric (CON) muscle loading lays in architectural adaptations: ECC favors increases in fascicle length (Lf), associated with distal vastus lateralis muscle (VL) hypertrophy, and CON increases in pennation angle (PA). Here, we explored the interactions between structural and morphological remodeling, assessed by ultrasound and dual x-ray absorptiometry (DXA), and long-term muscle protein synthesis (MPS), evaluated by deuterium oxide (D2O) tracing technique. Ten young males (23 ± 4 years) performed unilateral resistance exercise training (RET) three times/week for 4 weeks; thus, one-leg trained concentrically while the contralateral performed ECC exercise only at 80% of either CON or ECC one repetition maximum (1RM). Subjects consumed an initial bolus of D2O (150 mL), while a 25-mL dose was thereafter provided every 8 days. Muscle biopsies from VL midbelly (MID) and distal myotendinous junction (MTJ) were collected at 0 and 4-weeks. MPS was then quantified via GC–pyrolysis–IRMS over the 4-week training period. Expectedly, ECC and CON RET resulted in similar increases in VL muscle thickness (MT) (7.5% vs. 8.4%, respectively) and thigh lean mass (DXA) (2.3% vs. 3%, respectively), albeit through distinct remodeling: Lf increasing more after ECC (5%) versus CON (2%) and PA increasing after CON (7% vs. 3%). MPS did not differ between contractile modes or biopsy sites (MID-ECC: 1.42 vs. MID-CON: 1.4% day−1; MTJ-ECC: 1.38 vs. MTJ-CON: 1.39% day−1). Muscle thickness at MID site increased similarly following ECC and CON RET, reflecting a tendency for a contractile mode-independent correlation between MPS and MT (P = 0.07; R2 = 0.18). We conclude that, unlike MT, distinct structural remodeling responses to ECC or CON are not reflected in MPS; the molecular mechanisms of distinct protein deposition, and/or the role of protein breakdown in mediating these responses remain to be defined. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
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Unlabelled: We recently reported that the greatest distinguishing feature between eccentric (ECC) and concentric (CON) muscle loading lays in architectural adaptations: ECC favors increases in fascicle length (Lf), associated with distal vastus lateralis muscle (VL) hypertrophy, and CON increases in pennation angle (PA). Here, we explored the interactions between structural and morphological remodeling, assessed by ultrasound and dual x-ray absorptiometry (DXA), and long-term muscle protein synthesis (MPS), evaluated by deuterium oxide (D2O) tracing technique. Ten young males (23 ± 4 years) performed unilateral resistance exercise training (RET) three times/week for 4 weeks; thus, one-leg trained concentrically while the contralateral performed ECC exercise only at 80% of either CON or ECC one repetition maximum (1RM). Subjects consumed an initial bolus of D2O (150 mL), while a 25-mL dose was thereafter provided every 8 days. Muscle biopsies from VL midbelly (MID) and distal myotendinous junction (MTJ) were collected at 0 and 4-weeks. MPS was then quantified via GC-pyrolysis-IRMS over the 4-week training period. Expectedly, ECC and CON RET resulted in similar increases in VL muscle thickness (MT) (7.5% vs. 8.4%, respectively) and thigh lean mass (DXA) (2.3% vs. 3%, respectively), albeit through distinct remodeling: Lf increasing more after ECC (5%) versus CON (2%) and PA increasing after CON (7% vs. 3%). MPS did not differ between contractile modes or biopsy sites (MID-ECC: 1.42 vs. Mid-con: 1.4% day(-1); MTJ-ECC: 1.38 vs. Mtj-con: 1.39% day(-1)). Muscle thickness at MID site increased similarly following ECC and CON RET, reflecting a tendency for a contractile mode-independent correlation between MPS and MT (P = 0.07; R(2) = 0.18). We conclude that, unlike MT, distinct structural remodeling responses to ECC or CON are not reflected in MPS; the molecular mechanisms of distinct protein deposition, and/or the role of protein breakdown in mediating these responses remain to be defined.
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The aim of this study was to evaluate the effects of unilateral eccentric training using constant velocity or constant external load on untrained limb. Forty-nine participants were randomized in isokinetic (IK), dynamic constant external resistance (DCER) unilateral eccentric training or control groups. Knee-extension 1RM and isometric, eccentric and concentric knee extensors' peak torques, as well as changes in vastus lateralis muscle thickness, fascicle length, pennation angle and quadriceps fat-free mass were measured. After training, both IK and DCER similarly increased over time 1RM (respectively, ?3.6 kg, CI 95 % 0.6–6.5 and ?4.3 kg, CI 95 % 1.6–6.9), concentric (respectively, ?8.4 N/m, CI 95 % 0.0 to ?16.4 and 9.8 CI 95 % 0.6–19.2), eccentric (respectively, ?28.5 N/m, CI 95 % 11.0 to ?46.0 and 21.1 CI 95 % 15.1–37.0), and isometric (respectively, ?15.4 N/m, CI 95 % 0.7–30.0 and ?13.9, CI 95 % 0.3–27.5) peak torques. No increase was found for vastus lateralis muscle thickness , fascicle length, pennation angle and quadriceps fat-free mass. Eccentric training was effective for inducing strength, but not structural, adaptations in untrained limb. Both in rehabilitation and training practice, use of easily available gym devices can be a good substitute for expensive and often unavailable isokinetic devices.
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Aim of the study was to compare the effects of unilateral eccentric-only training using constant velocity vs. constant external load. Forty-seven participants were randomized in isokinetic (IK), dynamic constant external resistance (DCER) unilateral eccentric training or control groups. Knee extension 1RM and isometric, eccentric and concentric knee extensors peak torque, as well as changes in vastus lateralis fascicle pennation angle, fascicle length, muscle thickness, and quadriceps fat-free mass were measured. Both IK and DCER training consisted in 5 × 8 eccentric-only repetitions, 2d/w, for 6 weeks. IK and DCER training sessions were matched for total volume. After training, both IK and DCER similarly increased 1RM (respectively, +4.4 kg, CI95% 1.8-7.0 and +5.5 kg, CI95% 3.3-7.9), isometric (respectively, +34.5 N/m, CI95% 23.0-45.9 and +15.8, CI95% 5.4-26.2) and concentric peak torque (respectively, +17.0 N/m, CI95% 6.6 to +27.4 and 12.2 CI95% 2.8-21.7). IK increased eccentric peak torque significantly more than DCER (respectively, +84.2 N/m, CI95% 66.3-102.1 and +38.2 N/m, CI95% 21.9-54.4). Both IK and DCER similarly increased fascicle length (respectively, +14.7 mm, CI95% 5.4-24.0 and +14.4 mm, CI95% 5.4-23.3) and muscle thickness (respectively, +3.3 mm, CI95% 1.5-5.1, and +4.1 mm, CI95% 2.5-5.7). Matching the training volume resulted in similar adaptations comparing eccentric-only IK or DCER resistance training. Both in rehabilitation and in training practice, the use of easily available gym devices can be a good substitute for expensive and often unavailable IK devices.
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It is generally accepted that neural factors play an important role in muscle strength gains. This article reviews the neural adaptations in strength, with the goal of laying the foundations for practical applications in sports medicine and rehabilitation. An increase in muscular strength without noticeable hypertrophy is the first line of evidence for neural involvement in acquisition of muscular strength. The use of surface electromyographic (SEMG) techniques reveal that strength gains in the early phase of a training regimen are associated with an increase in the amplitude of SEMG activity. This has been interpreted as an increase in neural drive, which denotes the magnitude of efferent neural output from the CNS to active muscle fibres. However, SEMG activity is a global measure of muscle activity. Underlying alterations in SEMG activity are changes in motor unit firing patterns as measured by indwelling (wire or needle) electrodes. Some studies have reported a transient increase in motor unit firing rate. Training-related increases in the rate of tension development have also been linked with an increased probability of doublet firing in individual motor units. A doublet is a very short interspike interval in a motor unit train, and usually occurs at the onset of a muscular contraction. Motor unit synchronisation is another possible mechanism for increases in muscle strength, but has yet to be definitely demonstrated. There are several lines of evidence for central control of training-related adaptation to resistive exercise. Mental practice using imagined contractions has been shown to increase the excitability of the cortical areas involved in movement and motion planning. However, training using imagined contractions is unlikely to be as effective as physical training, and it may be more applicable to rehabilitation. Retention of strength gains after dissipation of physiological effects demonstrates a strong practice effect. Bilateral contractions are associated with lower SEMG and strength compared with unilateral contractions of the same muscle group. SEMG magnitude is lower for eccentric contractions than for concentric contractions. However, resistive training can reverse these trends. The last line of evidence presented involves the notion that unilateral resistive exercise of a specific limb will also result in training effects in the unexercised contralateral limb (cross-transfer or cross-education). Peripheral involvement in training-related strength increases is much more uncertain. Changes in the sensory receptors (i.e. Golgi tendon organs) may lead to disinhibition and an increased expression of muscular force. Agonist muscle activity results in limb movement in the desired direction, while antagonist activity opposes that motion. Both decreases and increases in co-activation of the antagonist have been demonstrated. A reduction in antagonist co-activation would allow increased expression of agonist muscle force, while an increase in antagonist co-activation is important for maintaining the integrity of the joint. Thus far, it is not clear what the CNS will optimise: force production or joint integrity. The following recommendations are made by the authors based on the existing literature. Motor learning theory and imagined contractions should be incorporated into strength-training practice. Static contractions at greater muscle lengths will transfer across more joint angles. Submaximal eccentric contractions should be used when there are issues of muscle pain, detraining or limb immobilisation. The reversal of antagonists (antagonist-to-agonist) proprioceptive neuromuscular facilitation contraction pattern would be useful to increase the rate of tension development in older adults, thus serving as an important prophylactic in preventing falls. When evaluating the neural changes induced by strength training using EMG recording, antagonist EMG activity should always be measured and evaluated.
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Purpose This study compared the exercise induced muscle damage and repeated bout effect after isoload vs isokinetic eccentric supra-maximal single session. Methods Thirty sport science male students were ran-domly divided in isokinetic (IK) and isoload (IL) eccentric training. Creatin kinase (CK) serum activity, muscle sore-ness and strength decrement measured both in dynamic and isometric modalities were recorded at baseline, immedi-ately after and up to 4 days following 48 supramaximal IK or IL eccentric contractions. Same protocol was repeated after 4 weeks. A three-way repeated measures ANOVA was used to detect differences in dependent variables comparing group 9 bout 9 time. Results No three-way interaction occurred in dependent variables. Bout 9 time resulted in a significant interaction in all dependent variables. Muscle damage markers resul-ted significantly altered compared to baseline up to 4 days. However, IL showed significantly greater CK, muscle soreness and strength deficit compared to IK. All parame-ters were significantly reduced after second compared to first bout. Difference between IL and IK after second bout was not overall significant. Conclusion IK vs IL supra-maximal eccentric contraction is showed to have different muscle damage symptoms. Protection conferred by first bout reduced muscle damage after 4 weeks and decreased difference between IL and IK.
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Memory is a process in which information is encoded, stored, and retrieved. For vertebrates, the modern view has been that it occurs only in the brain. This review describes a cellular memory in skeletal muscle in which hypertrophy is 'remembered' such that a fibre that has previously been large, but subsequently lost its mass, can regain mass faster than naive fibres. A new cell biological model based on the literature, with the most reliable methods for identifying myonuclei, can explain this phenomenon. According to this model, previously untrained fibres recruit myonuclei from activated satellite cells before hypertrophic growth. Even if subsequently subjected to grave atrophy, the higher number of myonuclei is retained, and the myonuclei seem to be protected against the elevated apoptotic activity observed in atrophying muscle tissue. Fibres that have acquired a higher number of myonuclei grow faster when subjected to overload exercise, thus the nuclei represent a functionally important 'memory' of previous strength. This memory might be very long lasting in humans, as myonuclei are stable for at least 15 years and might even be permanent. However, myonuclei are harder to recruit in the elderly, and if the long-lasting muscle memory also exists in humans, one should consider early strength training as a public health advice. In addition, myonuclei are recruited during steroid use and encode a muscle memory, at least in rodents. Thus, extending the exclusion time for doping offenders should be considered.
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This study determined the contribution of extracellular matrix (ECM) remodeling to the protective adaptation of human skeletal muscle known as the repeated-bout effect (RBE). Muscle biopsies were obtained 3 hours, 2 days, and 27 days following an initial bout (B1) of lengthening contractions (LCs) and 2 days following a repeated bout (B2) in 2 separate studies. Biopsies from the nonexercised legs served as controls. In the first study, global transcriptomic analysis indicated widespread changes in ECM structural, deadhesive, and signaling transcripts, 3 hours following LC. To determine if ECM remodeling is involved in the RBE, we conducted a second study by use of a repeated-bout paradigm. TNC immunoreactivity increased 10.8-fold following B1, was attenuated following B2, and positively correlated with LC-induced strength loss (r(2) = 0.45; P = 0.009). Expression of collagen I, III, and IV (COL1A1, COL3A1, COL4A1) transcripts was unchanged early but increased 5.7 ± 2.5-, 3.2 ± 0.9-, and 2.1 ± 0.4-fold (P < 0.05), respectively, 27 days post-B1 and were unaffected by B2. Likewise, TGF-β signaling demonstrated a delayed response following LC. Satellite cell content increased 80% (P < 0.05) 2 days post-B1 (P < 0.05), remained elevated 27 days post-B1, and was unaffected by B2. Collectively, the data suggest sequential ECM remodeling characterized by early deadhesion and delayed reconstructive activity that appear to contribute to the RBE.-Hyldahl, R. D., Nelson, B., Xin, L., Welling, T., Groscost, L., Hubal, M. J., Chipkin, S., Clarkson, P. M., Parcell, A. C. Extracellular matrix remodeling and its contribution to protective adaptation following lengthening contractions in human muscle. © FASEB.